CVE-2026-98503
In the Linux kernel, the following vulnerability has been resolved:
packet: use ubuf_info completion for TX_RING packets
tpacket_snd sends skbs with frags pointing into its ring slots. Slots are released when skb->destructor is called.
A call to skb_orphan calls skb->destructor before the skb is freed. This can cause the slot to be reused while still linked into the skb.
Switch to standard zerocopy completion (ubuf_info) so the slot is only released once all references to the payload are freed or copied. Restore skb->destructor to standard sock_wfree.
The ubuf_info completion callback can be called with a NULL skb, but only from net_zcopy_put and related API, used by zerocopy implementations that hold their own reference on the uarg, such as MSG_ZEROCOPY.
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This uarg is only ever completed from skb_zcopy_clear, so skb is always set.
To prevent userspace from aliasing in-flight state on shared ring slots, allocate tpacket_uarg per packet, rather than per slot. This adds a small allocation to the transmit path. Use standard kmalloc to allow backporting to stable kernels.
The uarg holds an sk_wmem_alloc reference, rather than an sk_refcnt reference. packet_free_tx_ring waits on sk_wmem_alloc before freeing the ring pages. Always allocate vec->deferred for tx_ring so page-backed rings also wait on sk_wmem_alloc when skb_copy_ubufs drops page refs before calling tpacket_ubuf_complete.
Drop the tx_ring.pg_vec test that tpacket_destruct_skb performed before accessing the slot. The sk_wmem_alloc reference now guarantees that the slot is valid. The test is also not sufficient by itself, as it reads pg_vec without pg_vec_lock, so it can race with packet_set_ring.
As a result a slot is released when its payload is copied, which can be before transmission (e.g., in skb_orphan_frags_rx). If copied before skb_tx_timestamp() is called, no slot timestamp is recorded, similar to when skb_orphan() was called early in the datapath before this patch.
Revert the now unused previous skb_zcopy_.._nouarg infra.
Depends on commit 992cc9f94ca9 ("net/packet: defer vmalloc TX_RING free until skbs finish").
CVSS
NVD hasn't assigned a CVSS score to this CVE (common since the April 2026 policy change).
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days
- 0.20 %
- Percentile among all scored CVEs
- 9
- Score date
- 10/20/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (1)
⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.
References
Show 4 references
Raw JSON (NVD)
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{
"id": "CVE-2026-98503",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5cd8d46ea1562be80063f53c7c6a5f40224de623",
"lessThan": "e67c455d79fbf709a94965f09a2be6bf4f4ba5fd",
"versionType": "git"
},
{
"status": "affected",
"version": "5cd8d46ea1562be80063f53c7c6a5f40224de623",
"lessThan": "eda9bcb721f15a93746a99eabda33d80b86404fd",
"versionType": "git"
},
{
"status": "affected",
"version": "5cd8d46ea1562be80063f53c7c6a5f40224de623",
"lessThan": "2a0c9afefc0ecea2cc30ccfbbbc98182a0986191",
"versionType": "git"
},
{
"status": "affected",
"version": "5cd8d46ea1562be80063f53c7c6a5f40224de623",
"lessThan": "9518405613863d0bf0700927a21367f5942cf058",
"versionType": "git"
},
{
"status": "affected",
"version": "67f6fba765ef8cb19089d476e3c367212a2fbdfd",
"versionType": "git"
},
{
"status": "affected",
"version": "f2a67e68dbaeae7c88e5522873d7b908911f9f77",
"versionType": "git"
},
{
"status": "affected",
"version": "4.14.86",
"lessThan": "4.15",
"versionType": "semver"
},
{
"status": "affected",
"version": "4.19.7",
"lessThan": "4.20",
"versionType": "semver"
}
],
"programFiles": [
"include/linux/skbuff.h",
"net/packet/af_packet.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.20"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.20",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.112",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.55",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.9",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"include/linux/skbuff.h",
"net/packet/af_packet.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-10-18T16:17:01.370",
"references": [
{
"url": "https://git.kernel.org/stable/c/2a0c9afefc0ecea2cc30ccfbbbc98182a0986191",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/9518405613863d0bf0700927a21367f5942cf058",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/e67c455d79fbf709a94965f09a2be6bf4f4ba5fd",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/eda9bcb721f15a93746a99eabda33d80b86404fd",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\npacket: use ubuf_info completion for TX_RING packets\n\ntpacket_snd sends skbs with frags pointing into its ring slots. Slots\nare released when skb->destructor is called.\n\nA call to skb_orphan calls skb->destructor before the skb is freed.\nThis can cause the slot to be reused while still linked into the skb.\n\nSwitch to standard zerocopy completion (ubuf_info) so the slot is only\nreleased once all references to the payload are freed or copied.\nRestore skb->destructor to standard sock_wfree.\n\nThe ubuf_info completion callback can be called with a NULL skb, but\nonly from net_zcopy_put and related API, used by zerocopy implementations\nthat hold their own reference on the uarg, such as MSG_ZEROCOPY. This\nuarg is only ever completed from skb_zcopy_clear, so skb is always set.\n\nTo prevent userspace from aliasing in-flight state on shared ring\nslots, allocate tpacket_uarg per packet, rather than per slot. This\nadds a small allocation to the transmit path. Use standard kmalloc to\nallow backporting to stable kernels.\n\nThe uarg holds an sk_wmem_alloc reference, rather than an sk_refcnt\nreference. packet_free_tx_ring waits on sk_wmem_alloc before freeing\nthe ring pages. Always allocate vec->deferred for tx_ring so page-backed\nrings also wait on sk_wmem_alloc when skb_copy_ubufs drops page refs\nbefore calling tpacket_ubuf_complete.\n\nDrop the tx_ring.pg_vec test that tpacket_destruct_skb performed before\naccessing the slot. The sk_wmem_alloc reference now guarantees that the\nslot is valid. The test is also not sufficient by itself, as it reads\npg_vec without pg_vec_lock, so it can race with packet_set_ring.\n\nAs a result a slot is released when its payload is copied, which can\nbe before transmission (e.g., in skb_orphan_frags_rx). If copied\nbefore skb_tx_timestamp() is called, no slot timestamp is recorded,\nsimilar to when skb_orphan() was called early in the datapath before\nthis patch.\n\nRevert the now unused previous skb_zcopy_.._nouarg infra.\n\nDepends on commit 992cc9f94ca9 (\"net/packet: defer vmalloc TX_RING\nfree until skbs finish\")."
}
],
"lastModified": "2026-10-19T10:19:03.490",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}